1. Field of the Invention
The present invention generally relates to personal computing devices (e.g., personal or laptop computers) in a Power over Ethernet (PoE) system, and more specifically to power classification and management of these devices in an enterprise environment.
2. Related Art
Ethernet communications provide high speed data communications over a communications link between two communication nodes that operate according the IEEE 802 Ethernet Standard. The communications medium between the two nodes can be twisted pair wires for Ethernet, or other types of communications medium that are appropriate. Power over Ethernet (PoE) communication systems provide power and data communications over a common communications link. More specifically, a power source device (e.g., power source equipment (PSE)) connected to the physical layer of the first node of the communications link provides DC power (for example, 48 volts DC) to a powered device (PD) at the second node of the communications link. The DC power is transmitted simultaneously over the same communications medium with the high speed data from one node to the other node.
The PSE device is often a data switch. Typically, a PSE on a switch is called an endspan device. The switch is typically a networking bridge device with data ports that can additionally have routing capability. The switch could have as little as two data ports or as many as 400 or more data ports. It may have two or more rows of data ports, where a data port in an input row of data ports can be switched to any one of the data ports in an output row of data ports. Each data port can include a serial-to-parallel (i.e. SERDES) transceiver, and/or a PHY device, to support high speed serial data transport. Herein, data ports and their corresponding links can be interchangeably referred to as data channels, communication links, data links, etc, for ease of discussion.
Typical PD devices that utilize PoE include Internet Protocol (IP) phones (Voice over IP (VoIP) phones), wireless access points, etc. Personal computing devices, such as personal or laptop computers, are another example of PD devices. The power requirements of personal computing devices are significantly different and often much higher than that of VoIP phones and wireless access points. For example, while VoIP systems can have unsubscribed power, personal computing devices in enterprise systems oversubscribe power. In addition, a personal computing device may change its power draw depending on its application load. Moreover, personal computing devices can power other devices such as USB devices or external drives, for example, which will affect total power draw.
The powering of personal computing devices using PoE in an enterprise environment places a tremendous noise and power density burden on a switch PSE. For example, in a conference room of ten people with laptops, a typical 10-port PoE switch would require approximately 25 watts (25 W) of PoE per port to go to each laptop. This totals 250 W, which can actually total more than 300 W if assuming an 80% AC/DC conversion efficiency. More may be required if one or more of the laptops are executing higher power applications, or powering a USB device, for example, or if trickle or regular charging is required. In addition, the switch itself needs approximately 2 W per port just for the data portion of the networking. As the number of ports increases, the power needs increase. Moreover, the cost of power supplies, cooling, and noise issues do not scale linearly, but instead progressively worsen with the increase in power.
In a typical PoE system, power for a PoE PD is classified using information regarding voltage, current draw, and the like, over a Layer 1 type physical communication layer. This is a one-way (i.e., from a PD to a switch), one-time (i.e., static) classification that occurs at the time of connection. The power classification determines how much power is needed by a PD. In an enterprise environment consisting of personal computing devices in which many of the devices could be demanding power all at one time, it is extremely difficult to manage the supply of power to each device and virtually impossible to adjust the supply of power as the power needs change.
What is needed is an intelligent PoE system in which the power supplied to multiple PoE personal computing devices can be dynamically and optimally classified and managed based on changing conditions while reducing noise issues, power supply cooling issues, and the overall cost of a switch by reducing the size of the power supply needed. Specifically, what is needed is a mechanism in an enterprise environment that dynamically classifies, allocates, and prioritizes, via one or more algorithms, for example, power supplied to PoE personal computing devices. A higher level of data communication support (such as data link layer (Layer 2) support) for such a mechanism is also needed.